In some prior art optical systems, when it was required to precisely match an input gaussian beam to the input requirements of an optical system, it was necessary to have two or more adjustable optical features in the design, and the optical elements required iterative adjustment as each adjustment of an individual optical element would affect the output waist diameter and the output waist location. Alternatively, another approach often taken was to give up on getting a really good match and to use a single adjustment to simultaneously change both waist size and waist location, but not independently.
Beam-shaping optical systems are well known in the art. U.S. Pat. No. 4,318,594 issued to Hiroshi Hanada on Mar. 9, 1982, discloses a beam-shaping optical system for treating or collimating the beam emitted from the exit surface of a semiconductor laser. U.S. Pat. No. 4,705,367, issued to Alan C. Eckbreth et al. on Nov. 10, 1987, is directed to a variable length optical system for generating a constant diameter focal spot.
A feature of applicant's invention, not found in the prior art, is the provision of a single movable lens in combination with a movable afocal pair (telescope) wherein the single movable lens serves as an input to the telescope to provide an optical system for matching the available gaussian input beam to the specific input requirements of some other optical system.
One example of such an optical system would be a system wherein the output of an argon laser is to be converted into the optimum input for the succeeding parts of a laser velocimeter system. Some laser velocimeter systems are disclosed in U.S. Pat. Nos. 4,148,585, issued on Apr. 10, 1979, to Bargeron et al.; 4,346,990, issued on Aug. 31, 1982, to Rhodes; and 4,697,922, issued on Oct. 6, 1987, to Gunter et al.
In such velocimeter systems, a relatively long "stack" of beam processing components, such as beam splitters (spacers), Bragg cells, etc., are used, and it is necessary to keep the beam small enough to negotiate the various apertures in the stack. The optical system of the present invention provides such capabilities.